Thursday, December 31, 2015

2016 Tennis ratings test: Melog vs. ATP

One of the obvious things to try when building a new sports ranking system is to compare it to the systems that are already out there. And while there are plenty of other statistical ratings in tennis, by far the most commonly-used measure is the official ATP rankings themselves.

So let's set up to see how the Melog system compares to the ATP's. This fairly unscientific study will involve choosing several pairs of players who are at least somewhat similar in type but whose rankings differ significantly and in opposite directions between the two systems, then seeing how they fare in comparison to each other over the next 12 months.

Since the ATP rankings are the generally-used standard, we'll be watching how the players fare by that measure next year. It's worth pointing out that the players the ATP rankings prefers will have a built-in advantage, because those are the rankings used to determine acceptance into tournaments and seedings within them; some of Melog's preferred players will have to face much tougher opponents much earlier in their draws.

It was SO tempting to compare Stan to Rafael Nadal, who I expect to have at least a partial comeback next year (say, making at least one Slam final). But Berdych is a fairer matchup, as they're close in age and have relatively similar levels of success overall (Stan has two Slams now, but Berdych has played at a top-10 level for much longer). Melog would expect Berdych to win out over the next 12 months - but it would have expected the same thing in 2015, and Stan's French Open title kept that from happening.

Both big servers. Isner is substantially older, but Raonic is coming off of an injury, and it's worth watching how he does for that reason alone; Melog is kinder to players who miss moderate amounts of time, but if his health issues recur, his ranking will suffer yet again.

Bautista Agut is one of the players on whom the two systems disagree most emphatically. It's another pair similar to Stan and Berdych, as Bautista Agut is more consistent and Cilic can reach a higher top level, which he proved quite thoroughly at the 2014 US Open. But that also means he may rely on a couple of big results to prop up his ranking, and if he falls short of them this year...

Kohlschreiber is another one of the biggest disagreements between the two systems, as Melog accounts for the fact that he spent all of last year running into impossible matchups early in his events. Lopez fared better against the top players (4-6 against top 10 competition to Kohlschreiber's 0-8), but also played far worse against subpar opponents (16-11 against foes outside the top 50, compared to 25-4 for the German).

This pairing will have the biggest chance of being warped by the initial difference in the ATP rankings, as Kohlschreiber is currently in position to be unseeded at the Australian Open, and when he didn't have a seed at Wimbledon last year, he drew Djokovic in the first round.

Two up-and-comers, both of whom have had promising results in different contexts; Thiem won three titles last year, while Kyrgios made his second Grand Slam quarterfinal. In this case, it's the ATP ratings that prefer the consistent player (whose titles largely came against unimpressive fields - Thiem had only 3 matches against top-10 opposition last year), and Melog that goes for the mercurial talent (who picked up a few very nice victories during the year, beating Federer, Raonic, and Wawrinka).

It's also worth pointing out that the Melog ratings may not handle clay specialists well, and Thiem is arguably one of those. Speaking of which...

Fognini has long had a tendency to get blown out when not playing on clay, which hurts him in the Melog ratings. (In particular, he had a losing record on hard courts against players ranked outside the top 100. One of those was Juan Martin del Potro, who's not your average non-top-100 player, but he was still 2-3 apart from that match.) Muller, on the other hand... I'm honestly not entirely sure what Melog is seeing here (even if he does have a solid record against second-tier opponents). But I suppose we'll find out.

I'm not entirely sure why Melog frowns on Paire's remarkable comeback season to this extent, but if I had to guess, I'd say it's because he relied on third sets (or fifth sets) so much. In matches that went to a decider, Paire went 27-9 (Chung, by comparison was 12-10). In straight-set decisions, Paire was a comparatively tame 34-17 (42-13 for Chung, albeit against mostly Challenger competition).

Chung is an interesting test case on his own; he had a tremendous season in Challengers at a young age, and the players who've done that have usually ended up with excellent careers - but they haven't always been excellent right away. The transition to the World Tour level can be a tough one, especially for someone who's not regarded as having a lot of big weapons.

For the most part, I've tried to pair up players who are at similar stages in their careers. The last three pairs won't meet that criteria at all - but not all in the same direction, which should help the effects cancel out.

Verdasco is not a young player, and is largely regarded as being past his prime; Coric, on the other hand, is a promising youngster. Their records were similarly mediocre on the ATP level last year (26-28 for Coric, 24-26 for Verdasco). So why does Melog like Verdasco so much more?

It doesn't look like it's necessarily success against different levels of player; Verdasco was 3-13 against ATP top 20 opponents to Coric's 2-12, and 16-4 against players outside the top 50 to Coric's 18-3 (in World Tour matches only). Coric's draw grades out as somewhat easier, but that's likely in part because he played a Challenger after a first-round loss at the US Open (to Nadal, despite taking a set), and he won the Challenger.

But despite Coric's Challenger win, his raw results were slightly worse; Verdasco won over half of the service games he played this year, and Coric was somewhat below .500 in that regard. Combine that fact with Coric's slightly weaker draw, and you apparently get a pretty big difference in Melog rating. The question will be whether that holds up going forward.

Dodig is an interesting one here, because he spent much of the year playing qualifying matches, which aren't counted in the Melog system. (His results in those matches were not bad; even if he often didn't make it all the way through, the losses were usually to good players.) He was a decent 8-11 in ATP main draws, but his best work came at the next level down, as he went 22-4 in Challengers with three titles, including a season-closing victory at Andria without dropping a set.

Klizan, on the other hand, spent almost the entire season at the World Tour level, posting a solid 30-27 record and winning a title - but he also manged to avoid high-level competition almost completely, playing only 8 of his 57 matches against opponents ranked in the top 20 (he went 2-6). In fact, less than half of his matches were against players in the top 50, and he went 6-17 in those matches; even players outside the top 50 were a challenge, as his 24-10 mark in those matches is fine, but not terribly impressive.

The only thing these two players have in common is that they sometimes go by three names. Apart from that, Fritz is either the youngest player in the top 200 or very close, and Estrella this year became (I believe) the oldest first-time title winner in ATP history. Estrella is a clay specialist, while Fritz played no professional matches on dirt this year (though he did make the final of the Junior French Open, which is not counted in either rating system).

Given that he's in the top 200 on the strength of only eight events, I would very much expect Fritz to join the top 100 this year if he plays a full season. Whether that'll be enough to push him ahead of Estrella, only time will tell.

Which I suppose is true of the rest of the pairings as well. Bring on the season!